Comment on: "New" lunar meteorites: Impact melt and regolith breccias and large-scale heterogeneities of the upper lunar crust, by P. H. Warren, F. Ulff-Mller, and G. W. Kallemeyn

Abstract

We described lunar meteorite Dhofar 026 (Cohen et al. 2004) and interpreted this rock as a strongly shocked granulitic breccia (or fragmental breccia consisting almost entirely of granuliticbreccia clasts) that was partially melted by post-shock heating. Warren et al. (2005) objected to many aspects of our interpretation: they were uncertain whether or not the bulk rock had been shocked; they disputed our identification of the precursor as granulitic breccia; and they suggested that mafic, igneous-textured globules within the breccia, which we proposed were melted by post-shock heating, are clasts with relict textures. The major evidence for shock of the bulk rock is the fact that the plagioclase in the lithologic domains that make up 80-90% of the rock is devitrified maskelynite. The major evidence for a granulitic-breccia precursor is the texture of the olivine-plagioclase domain that constitutes 40-45% of the rock; Warren et al. apparently overlooked or ignored this lithology. Textures of the mafic, igneous-textured globules, and especially of the vesicles they contain, demonstrate that these bodies were melted and crystallized in situ. Warren et al. suggested that the rock might have originally been a regolith breccia, but the textural homogeneity of the rock and the absence of solar windderived noble gases preclude a regolith-breccia precursor. Warren et al. classified the rock as an impact-melt breccia, but they did not identify any fraction that was impact melt.